Evolutionary Perspectives

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Evolutionary Perspectives

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University of Southern California
Bisc 307l - General Physiology
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BISC 307L 1st Edition Lecture 1 Current Lecture What is evolution?  Descent with modification  Outcome is an organism matched to its environment o Matching during evolution optimizes reproductive success  Matching optimizes REPRODUCTIVE success o Called FITNESS- the probability that one's genes will be passed on to the next generation o Results within a population optimizes the average fitness within a particular environment o Will not optimize life span  Evolution does not optimize lifespan or general health  Natural selection is driving force Mechanisms of evolution- Darwin’s observations  1. Species produce more offspring than the environment can support  2. There is always variation within a population with the ability to compete for resources, survive, and reproduce  3. Some variation is inherited o Due to 3 sources  1. Mutations  2. Recombinations  3. Epigenetic modifications  (4). Developmental Plasticity  environment affects phenotype during development and also nervous system  Because of these observations..  4. Differences that produce offspring in more successful forms will be more prevalent- natural selection  5. Selection will lead to change in the population evolution (micro or macro) Natural Selection is NOT equal to survival of the fittest  Selection maximizes reproductive fitness, not health or longevity o Cant apply these principles to social aspects of life o ONLY REPRODUCTIVE FITNESS o Survival of genes not survival of health or well being  Evolutionary success of humans does not require long life o Before, people did not live long enough to contract the diseases we contract now o Historical life span of humans makes sense if we look at human fertility with age o Puberty is happening earlier and earlier o Reproductive health peaks in 20’s o Reproductive disease affects people in their 20s- Natural selection therefore optimizes things that occur during reproductive life only  Heart Failure- if our body is such a great system why is it designed to blow up?  Because disease of middle and advanced life  These mechanisms work well in young reproductive people Examples of Evolutionary “Flaws”  Humans are bipedal and have large brains o Evolution results in compromises  Bipedalism requires narrow pelvis vs. newborn survival requiring large head  Narrow pelvis is not good for reproduction  Big brain means babies head is big  Babies are altricial- meaning they need extended parental care  We are unusual because we stand up and have large brains o Why is this important?

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